Dyson Hickingbotham

Refinements in Microinstrumentation for Vitreous Surgery

We developed a series of 25-gauge (0.5 mm) microinstruments for vitreous surgery, including a 25-gauge vitreous cutter, 25-gauge microscissors for limited reuse, and a vitreous membrane dissector. Clinical experience with these instruments in more than 20 cases of advanced proliferative vitreoretinopathy, retinopathy of prematurity, and diabetic retinopathy indicates that these instruments facilitate delicate vitreoretinal dissections, particularly in the vitreous base and when fibrovascular tissues are closely adherent to the retina. Because of their smaller size, the microinstruments are more precise in their cutting capabilities than other instruments.

Clinicopathologic Correlation of Surgically Removed Macular Hole Opercula

Purpose To determine the ultrastructural characteristics of the operculum associated with macular holes. Methods We developed instrumentation and a technique to capture the operculum observed with macular holes. Two opercula were studied by transmission electron microscopy. Results The two specimens were attached to a layer of native collagen identified as cortical vitreous and were composed primarily of Mueller cells and fibrous astrocytes without adjacent inner limiting membrane. No distinct retinal neuronal tissue was present. Conclusions Our findings indicate that proliferation of fibrous astrocytes and Mueller cells occurs with the formation of a macular hole, that this reparative tissue may be dislodged, and it is the reparative tissue that previously has been interpreted as an operculum.

Temporary Keratoprosthesis for Use During Pars Plana Vitrectomy

We have developed a series of temporary keratoprostheses that permit closed pars plana vitrectomy in eyes with abnormal corneas. These devices are placed into a trephined opening in the cornea, and provide a clear, stable view of the intraocular contents. Immediately after vitrectomy, the keratoprosthesis is replaced with a corneal graft. We have used this technique successfully in four eyes with opaque or severely traumatized corneas.

Experimental Transvitreal Cyanoacrylate Retinopexy

We used an experimental rabbit model of rhegmatogenous retinal detachment to compare the onset, quality, and duration of chorioretinal adhesions obtained by transvitreal application of N-butyl-2-cyanoacrylate mixed with iophendylate with those obtained by transscleral retinal cryopexy. The chorioretinal adhesions produced by the cyanoacrylate tissue adhesive were immediate in onset, stronger, and long lasting.

The Three-Port Microcannular System for Closed Vitrectomy

Microcannulas used during vitreous surgery protect the entry site, avoid vitreous base damage, and allow easy exchange of 20- and 19-gauge (0.9- and 1-mm) instruments. The use of three cannulas of equal size permits interchangeability of all instruments. A locking mechanism allows attachment and exchange of various infusion lines (balanced salt solution, gas, and oil). Temporary plugging of the cannula is possible. Selection of 1 mm as a standard diameter for all cannulas make multiple-function instruments feasible.

Accuracy of topographic measurements with the optic nerve head analyzer

We used a plastic model of the human eye to study the accuracy with which the Optic Nerve Head Analyzer estimates the surface contour and two-dimensional size of the optic nerve head. Computer-generated contour lines were similar to the actual cross-sectional contour of plastic cups as photographed by scanning electron microscopy. The magnification error of computer-measured cup diameters was inversely related to the axial length of the model. The slope of this relationship was reduced with the use of either refraction or axial length as a correction factor for magnification error. Of the two correction factors, the former provided the closest estimation of the known diameters in the phakic model, while the latter performed better in the aphakic model.

Automated Fluid-Gas Exchange

Internal fluid-gas exchange with simultaneous fluid aspiration and gas injection is an important technique in complex posterior segment vitreous surgery. The various methods of injecting gas into the eye include a hand-activated or mechanically driven syringe,1 using the hydrostatic pressure of an intravenous bottle to drive gas out of a second inverted bottle,2 and a motorized syringe injector. 3

Diamond-Coated All-Purpose Foreign-Body Forceps

A new foreign-body forceps with diamond-coated jaws can grasp and hold intraocular foreign bodies of any shape and composition. A self-closing mechanism holds the material once grasped.

In vitro videographic comparison of argon and Nd:YAG laser iridotomy

We used an in vitro technique with high-magnification video recording to evaluate from the posterior side of the iris the immediate sequence of events during argon and Nd:YAG laser peripheral iridotomy. The observed effects differed strikingly. The argon laser caused a gradual mounding up of iris pigment epithelium with each successive energy application before final penetration. This effect was reduced but not eliminated with higher power levels. The Nd:YAG laser caused complete disruption and dispersal of the pigment epithelium with a single pulse of energy. Additionally, a multiple focal point configuration of the Nd:YAG laser was observed to produce a significantly larger iridotomy than a single focal point configuration for comparable energy settings. These observations may in part explain the observed clinical advantage of the Nd:YAG laser over the argon laser for creation of a patent iridotomy.

New Scleral Plugs for Use During Vitrectomy

We have devised two new scleral plugs for use in vitreous surgery when intraocular pressure is not maintained by the original 20-gauge plug as the incision stretches. Modification of the configuration of the heads of the plugs facilitates their identification during surgery, without hindering the surgeons ability to handle them with scleral plug forceps.